MathDox - A System for Interactive Mathematics Arjeh Cohen, Hans Cuypers, Jan Willem Knopper, Mark Spanbroek, Rikko Verrijzer Department of Mathematics and Computer Science Eindhoven University of Technology P.O. Box 513, 5600 MB Eindhoven, The Netherlands [email protected] Abstract: We discuss the MathDox system, a system for presenting highly interactive mathematical documents. The system consists of both an XML format for interactive mathematical documents as well as a server for these documents called the MathDox Player. Many of today©s web pages are dynamic and interactive in the sense that they adapt to the user and offer the user some control over the contents of the page. Examples of such web pages are eBanking, auction and eLearning sites. At mathematical websites, however, the dynamics and interactivity are often limited. We see three main reasons for this. First of all, interactivity in mathematical content often requires non-trivial computations that are not easily performed without specialized mathematical software. Secondly, displaying mathematics properly on a web page can be challenging. Modern browsers have only limited support for rendering mathematics. Third, the input of mathematical expressions is a difficulty. It requires specialized software that is not yet readily available. To address these issues we have developed the MathDox system. It consists of a format and a player. The MathDox format is an XML based language for interactive mathematical documents. MathDox documents can be transformed into web pages by the MathDox Player. These web pages are dynamic and interactive, support rendering of mathematics, offer easy access to computer algebra systems, and are equipped with a convenient mathematical input system. MathDox shows its potential when demonstrating algorithms, testing skills with exercises, or explaining new concepts with dynamic on-screen calculations. However, it can also be used for publishing static mathematical documents on paper or on the web. In the following sections we will introduce the MathDox system. First we describe the design goals we have formulated for our system. Then we examine the different XML formats that are combined in the MathDox format. Section 3 ªMathDox Toolsº discusses how the MathDox system functions and how interactivity and rendering of mathematics in browsers and on paper is achieved. We end by giving some examples of MathDox used in practice. Goals In this section, we briefly discuss the three main design goals we have set for our Mathdox system and discuss how we have set up the MathDox system to reach these goals. Interactivity A user needs means to interact with the mathematical content of an interactive document. This can vary from performing computations, checking answers to exercises or creating and manipulating graphs of functions. MathDox combines existing interactivity of web pages with the power of mathematical computations, resulting in interactive mathematics. This is achieved by making use of a scripting language and interfaces with external software, notably computer algebra systems. After user actions, pages are updated with new parameters and web services will be triggered to provide output needed for preparation of the new page. This results in adaptable pages and on the fly computations. One Source, Many Views An electronic format for interactive mathematics is best served in an electronic environment. However, there is no reason to limit documents to just one presentation form. It will often be useful to have such a document available in various formats, ranging from, for example, HTML, Word, ODF or PDF to LaTeX. Therefore we have chosen to separate the sources from the presentation of the document. We have done so by choosing XML as our source format. By the use of XSL transformations MathDox sources can be translated into various other formats, including HTML, PDF and LaTeX, and into various styles. Semantic Representation of Mathematics In order to achieve interactivity of the user with various mathematical services, the mathematics in an interactive document has to be represented in a unambiguous way. When mathematical notions appear, one should be able to trace their definition, when variables appear, it should be clear what their types, values, and dependencies are. For this reason, MathDox offers the possibility to represent the mathematical formulae and expressions in OpenMath (http://www.openmath.org/) or (content) MathML (http://www.w3.org/TR/MathML/), semantically rich XML- encodings of mathematics. The MathDox Format MathDox combines in a modular way various existing XML formats best suited for our purposes. Each format contributes a useful facet for interactive documents. The MathDox format itself is XML based, which makes it possible to use existing XML-tools on MathDox documents. The XML formats used in MathDox are: DocBook (http://www.oasis-open.org/docbook/), used for the global structure of documents. OpenMath (http://www.openmath.org/), for semantic encoding of mathematics. XForms (http://www.w3.org/MarkUp/Forms/), for user driven interactivity. Jelly (http://commons.apache.org/jelly/), a programming and scripting format. XInclude (http://www.w3.org/TR/xinclude/), for separating functionality in to several files. These formats will now be discussed individually. DocBook DocBook is a well-known documentation standard. Its logical structure facilitates searching and parsing of specific elements, enabling easy translation into other formats including HTML and PDF. This makes DocBook suitable for our needs. OpenMath, Semantic Encoding of Math Within MathDox mathematics appears in various forms: Mathematics as used in computations by software packages or mathematics solely meant for the user to read or sometimes for both the computer and the user. For each type of usage one wants mathematics to have specific properties. In general a user will be able to grasp the meaning behind a, possibly ambiguous, mathematical expression. Computer software, however, will need its mathematics to be completely unambiguous, since it cannot benefit from the context in the way a mathematically skilled reader does in order to solve gaps caused by incompleteness and ambiguity. OpenMath has been chosen as the main format for mathematics within MathDox documents. It is well suited because it is semantically rich, unambiguous, XML-based and can easily be transformed into other formats, such as MathML and LaTeX, which are better suited for presentation. These transformations allow MathDox documents to use OpenMath where semantics are important and switch to MathML or LaTeX, when the mathematics need to be presented to the user either on screen or on paper. The semantic information available from the OpenMath expressions enables easy translations between OpenMath and application specific syntax. At the moment MathDox supports interaction with the computer algebra systems Mathematica (http://www.wolfram.com/), Maple (http://www.maplesoft.com/), GAP (http://www.gap-system.org/), Maxima (http://maxima.sourceforge.net/), Wiris (http://www.mathsformore.com/), Magma (http://magma.maths.usyd.edu.au/) and Singular (http://www.singular.uni-kl.de/) and the dynamic geometry systems GeoGebra (http://www.geogebra.org/) and Cinderella (http://cinderella.de/). See also (Caprotti, Cohen, Cuypers, Riem & Sterk, 2000). XForms: User Driven Interactivity XForms in MathDox documents supplies a means of interaction with the reader of the MathDox document. It allows for many interaction (form) elements which can be used for user input, such as text fields, radio buttons, and drop down menus. In MathDox the XForms elements are used to trigger interaction with mathematical services like computer algebra systems. XForms is a recommendation of W3C and a successor to HTML-Forms. XForms is included into the XHTML 2.0 draft specifications. At this moment XForms is not yet properly supported by browsers, but work in this direction is in progress. For now the XForms code in MathDox documents is translated automatically by the MathDox Player into HTML forms supplemented by JavaScript. This translation is done by Orbeon Forms (http://www.orbeon.com/). Jelly: Programming and Scripting To specify and fine-tune reactions of a MathDox document to user input, an author needs programming constructs. For this purpose Jelly (http://commons.apache.org/jelly/) has been included in the MathDox format. Jelly is a JSP- like XML-language (http://java.sun.com/products/jsp/), and has been developed as part of the Apache project (http://www.apache.org/). Jelly can be used for conditional statements, loops, variables, calls to Java (http://java.sun.com/) objects and calls to web services. For example, the input of a user can be inspected with the use of the Jelly to see whether it has the needed structure, setting certain parameters to trigger specific reactions. XInclude: Separating Functionality in MathDox Files MathDox documents do not need to be a single big file. There are cases in which it is advantageous to split documents into smaller parts. The resulting set of parts will increase possibilities for reuse and support maintainability. XInclude is used to include and group together XML components from different files. XInclude is a W3C recommendation. MathDox Software So far we only discussed the MathDox format and just briefly mentioned the server-side software responsible for processing of this format. In this section we discuss the MathDox software. The MathDox Player The MathDox